Supporting means for speaker voice coils



Ma -ch 10, 1942. I J. M. ANDRUS 2,275,598

h SUPPORTING MEANS FOR A SPEAKER VOICE COIL Filed Aug. 7, 1939 F'atentecl Mar. 10, 1942 UNITED STATE SUPPORTING MEANS FOR SPEAKER VOICE COILS Joseph M. Andrus, Chicago, 111., assignor to Utah Radio Products Company, Chicago, 111., a corporation of Illinois Application August 7, 1939, Serial No. 288,786

3 Claims.

The invention relates to supporting means for a speaker voice coil and has as its general aim the provision of new and improved means for effectively supporting a voice coil assembly which is efficient and economical.

Supporting means for voice coil assemblies, sometimes termed spiders must have substantial rigidity in a plane normal to the axis of the voice coil for maintaining a proper spacing of the voice coil in the magnetic gap of the speaker. The supporting'means must also have substantial flexibility in a direction axially of the voice coil to permit the coil and the parts assembled therewith to respond to fluctuations in the ma netic fleld. Furthermore, the supporting means should be so fashioned that air may pass freely through the supporting means.

An object of the invention is to provide a new and improved supporting means for a voice coil assembly adapted to be secured to the assembly on a plane normal to the axis thereof and having substantial rigidity in and flexibility transversely of said plane, and in which a' large number of small perforations are thickly dispersed over the supporting means preferably in the arrangement of the interstices of a loosely woven material.

Another object is to provide a novel voice coil supporting means in which the separate elements of a loosely woven material are bonded together and the interstices of the material are open whereby a sheet of the material has an open grid form substantially rigid in the plane of the sheet and flexible in a direction transverse to said plane.

Other objects and advantages will become apparent in the following description and from the accompanying drawing, in which:

Figure 1 is a fragmentary front view of the central portion of a speaker having associated therewith a voice coil supporting means embodying the features of the invention.

Fig. 2 is a perspective view of a voice coil assembly and the supporting means.

Fig. 3 is a face view on a greatly enlarged scale of a section of the material from which the supporting means is fashioned.

Fig. 4 is a transverse sectional view through a sheet of such material.

While the invention is susceptible of various modifications and alternative constructions, I have shown in the drawing and will herein describe in detail the preferred embodiment, but it is to be understood that I do not thereby intend to limit the invention to the specific form disspaced relation to the pole faces.

closed, but intend to cover all modifications an alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

In the drawing, the numeral l0 designates generally the central portion of a conventional type of speaker frame. As is well known, a voicecoil assembly, comprising a cylindrical member II on which the voice coil (not shown) is wound, must be supported with respect to the magnetic gap of the speaker so that the voice coil is in properly In the present instance, the voice coil supporting means has been illustrated as being in the form of a circular. member I2 which is centrally apertured to surround the cylinder of the voice .coil assembly and to be secured thereto as by means of an axially extending flange l3 (Fig. 2). Peripherally, the member I2 is adhesively bonded or otherwise suitably secured to the frame.

The voice coil supporting means extends in a plane normal to .the axis of the voice coil and, since the spaced relation of the voice coil in the magnetic gap must be preserved, the supporting means must be substantially rigid in its plane yet it must have substantial flexibility transversely of its plane or in the direction of the voice coil axis to permit the voice coil to respond accurately to magnetic variations. If desired, the flexibility of the supporting means may be increased by providing near its outer periphery an annular rib M. It is important that movements of the voice coil be substantially unimpeded and for this reason voice coil supporting means have heretofore had various shapes and forms for minimizing the resistance offered by air to movement of the voice coil supporting means.

The present invention provides voice coil supporting means having substantial rigidity in its plane and flexibility in a direction transversely thereof. Moreover, the supporting means has a large number of closely spaced small perforations over its surface area permitting substantially unmaterially afiecting its transverse flexibility and without closing the interstices of the fabric.

In obtaining these results, I prefer to employ a material fashioned from a regenerated cellulose, for example, cellulose acetate of the type I Example 2 used in the material which is known commerv Parts cially as Celanese. The regenerated. cellulose Acetone 2 should have the property of being soluble and Cellulose" acetate 1 of returning substantially to its original state Petroleum ether 2 upon evaporation of the solvent. It is preferred Example 3 that a thermo-plastic cellulose acetate be used Parts some; the airial flange I 3 and the annular rib Methyl acetate 3 Il may be quickly and conveniently formed in a Dichlor ethyl ether 1 die by the application of heat and pressure. The. carbon tetrachloride 1 cellulose acetate "Celanese" is readily soluble in anumber of well known solvents and is thermo- After the material has been fluxed and dried p1astic to produce its unitary rigid structure, it may, "c may b t i i th form of n if desired, be moisture proofed in any suitable open mesh woven fabric 'andeach strand of the manner as by'applying a thin coating of w x o fabric is made up of a number of smaller threads. e e a S a d Impregnation 0f the mate- According to the process, the material is subrial wi a f r per cent. (4%) solution OffHEIO jected' to the action of a fiuxing agent capable wax in carbon tetrachloride will satisfactorily of softening each of the separate and individual m is e proof the materialelements and causing them to fiux or bond to- After the e a s be fi dried and gether. As a result, the individual small threads mo stu e p oofed, t ay e u o a e ed o in each fabric strand, as well as the fabric such as the circular disk-shown in the drawing. strands, are united integrally and produce a and thereafter subjected to a forming operation sheet of material having substantially the struco P od c t e axial flange l3 a d the bead ture shown in greatly exaggerated form in Figs. 3 h Operation y e Conveniently performed d 4, I th fi r th u it tra d r by subjecting the material to the combined action indicated at l5 and the open interstices at iii. of eat a d p s u n suitably formed dies- As examples of satisfactory cellulose acetate Where the material is celanese the p solvents, ethyl acetate, acetone and methyl aceu e a d pr ssu s qu d p p y to fo m t tate may be mentioned, However, these 501- 3() material may be Varied within ratherwide limits vents act so rapidly on the material that it is as long as h p re nd pressure are quite di fiicult as a practical matter to control a ed v s y- For p a combination of the fluxing action with any degree of uniformity. a p essure f 5 p u ds at may e vari d I refer, therefore, to use as an ingredient of the to a omb nat n f 500 unds pressur at fiuxing agent some substance which in a sense 1 dilutes the solvent in that the solvent action is I claim as my invention: I retarded or delayed. As retarding agents, I l. A support for a speaker voice coil compris-- have found that petroleum ether and carbon ing a sheet of open Weave fabric formed of an tetrachloride give satisfactory results. A fluxing inherently thermoplastic material having the inagent composed, for example, of ethyl acetate 40 dividual elements of each thread permanently or acetone with petroleum ether or of methyl bonded together and having each thread peracetate with carbon tetrachloride may be satismanently bonded to the other threads at each factorily used to produce the desired fluxing of point of crossing, said support having been subthe individual elements of a Celanese material. jected to a final forming operation under heat In the fluxing operation, it is noted that there and pressure and being characterized by substanmay be a tendency of such cellulose acetate as is tial rigidity in the direction of its plane and flextaken into solution to form an almost invisible ibility in a direction transverse to said plane. film across a considerable proportion of the in- 2. A support for a speaker voice coil compristerstices of the material, I have found that this ing a sheet of thermoplastic cellulose acetate madiillculty may be avoided by adding to the fiuxterial formed of a plurality of threads woven into ing agent a quantity of a cellulose acetate solvent a mesh fabric, the individual elements of each having a relatively slow evaporating rate which thread and the cross portions of all threads being is effective, theoretically, to reduce the surface permanently bonded together to provide a sheet tension ofthe dissolved celluloseacetate. Hence, rigid in the direction of its plane and flexible in as the fiuxed material is dried, the film across the a transverse direction, said support having been interstices will collapse and the interstices will molded into final form by heat and pressures remain open. Among the suitable solvents for 3. A spider for supporting the voice coil of a cellulose acetate which have a slowrate of evapradio loud speaker comprising a corrugated celluoration are Cellosolve acetate and dichlor ethyl lose acetate material formed of a plurality of ether. 1 00 threads woven into a fabric bonded together and The following formulas are cited as examples molded into corrugated form by heat and pres-' of fluxing agents which will produce the desired sure, the individual elements of each thread and results in a material formed of the cellulose acethe crossing portions of all threads being pertate, Celanese," the proportions being measured manently bonded and the weave of the fabric by v l 05 being such as to provide openings in the inter- Ea'ample 1 stices thereof after bonding, said spider being 7 Parts relatively rigid in the direction of its plane and Ethyl acetate.. 4 relatively flexible in a transverse direction. Cellosolve acetate 1 Petroleum ether 1- JOSEPH M. ANDRUS; 

